Silence in tax office doctrine amounts to a religion (9)
I believe the answer is:
shintoism
'to a religion' is the definition.
(Shintoism is an example)
'silence in tax office doctrine' is the wordplay.
'silence' becomes 'sh' ('sh' is said to tell someone to be silent).
'tax office' becomes 'to' (this could be a standard abbreviation which I don't know about).
'doctrine' becomes 'ism' (suffix for disciplines or schools of thought).
'sh'+'in'+'to'+'ism'='SHINTOISM'
'amounts' is the link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for shintoism that I've seen before include "Japanese religion" , "foreign religion" .)